John James Trengove was born in Stellenbosch on 3 October 1919. He is married to Izabel (formerly Erasmus). They have four children and fourteen grandchildren.
Trengove matriculated at Stellenbosch Boys’ High School (now Paul Roos Gymnasium) in 1936. He graduated from the University of Pretoria (as an extra-mural student) with a BA Degree (cum laude) in 1944 and his LLB degree (cum laude) in 1946.
From 1946 to 1966 Trengove practiced as an advocate, becoming Senior Counsel in 1960. During this period he served on the Pretoria Bar Council (as Chairman in 1966) and also on the General Council of the Bar of South Africa.
From 1967 to 1978 he served on the Transvaal Provincial Division of the Supreme Court and on the Appellate Division from 1978 to 1986.
After taking early retirement at the end of 1986 he served on the Courts of Appeal of Lesotho and Swaziland and also as an Acting Judge on the High Courts of Botswana, Namibia and for one term on the Constitutional Court of South Africa.
- National President of FAMSA (National Council for Marriage and Family Life) for about five years.
- National Chairman of NICRO (National Institute for Crime Prevention and Rehabilitation of Offenders) for about two years.
- Member of the Board of Trustees the Legal Resources Trust.
- Member of the Council of the University of Pretoria, as donor representative, for seventeen years, and was and still is, an assessor member of the Faculty of Law of the University of Pretoria.
- Set up the Office of the Judicial Inspectorate, and served as the first Inspecting Judge for a period of three years.
- Awarded a LLD Degree (Honoris Causa) at the University of Pretoria, and a Laureate Award by the Association of Alumni of the University of Pretoria.